A urinary tract infection (UTI) is the presence of bacteria in the urinary tract. UTIs are commonly classified as complicated and uncomplicated. Uncomplicated UTIs are usually due to a structural or functional abnormality. Signs and symptoms of an uncomplicated UTI include pain when urinating, urgency, frequency, awakening from sleep to go urinate and blood in the urine (most commonly in women). Complicated infections are more severe and involve the upper urinary tract. In men, UTIs are rare and always considered complicated. Signs and symptoms of a complicated UTI include nausea, vomiting, fever, flank pain and discomfort. Many classes of antibiotics can be given to treat a UTI and should be chosen according to their activity against the infecting bacteria.
Trimethoprin-Sulfamethoxazole
Trimethoprin-sulfamethoxazole (generic of Bactrim, Cotrim and Septra) is a combination antibiotic given as a three-day course. A one-day course produces fewer side effects but may be less effective than the three-day course; courses of 7 to 10 days do not have any added benefit. This medication should be avoided in patients who have an allergy to sulfa drugs. According to "Pharmacotherapy: A Pathophysiologic Approach," trimethoprin-sulfamethoxazole is found in high concentration in urinary tract tissue and the urine, which allows the drug to reach the infection directly--particularly in complicated infections. This medication may be used for the treatment of recurrent UTIs and is effective as prophylactic (preventative) therapy.
Penicillins
Penicillins, including ampicillin, amoxicillin-clavulanate (Augmentin) and carbenicillin, can be used for treatment of UTI. According to the University of Maryland Medical Center, amoxicillin is ineffective against bacteria called E.coli, limiting its use in a UTI caused by the bacteria. Amoxicillin-clavulanate is preferred for drug-resistant cases. Ampicillin may also work on a broad range of bacteria and may be useful for many UTIs.
Cephalosporins
Cephalosporins are used in cases of resistance to standard therapy, ampicillin and trimethoprin-sulfamethoxazole. However, there are no major advantages of the cephalosporins over the standard medications used to treat UTIs, and they're more costly. Cephalosporins indicated for the treatment of UTI include cephalexin, cefaclor, cefadroxil, cefuroxime, loracarbef and cefixime.
Fluoroquinolones
Fluoroquinolones used for treating UTIs include ciprofloxacin, norfloxacin, levofloxacin and ofloxacin. These antibiotics are used as alternatives to trimethoprin-sulfamethoxazole and are effective for upper urinary tract infections. These medications cannot be given in pregnancy and are avoided in children.
Tetracyclines
Tetracyclines include tetracycline, doxycycline and minocycline. This class of antibiotics is effective for initial episodes of UTIs but has limited use. Bacteria quickly develop resistance to these antibiotics and may lead to candidal (fungal) overgrowth. Furthermore, tetracyclines are contraindicated in children younger than 8 and during pregnancy.
Aminoglycosides
Aminoglycosides used for UTIs are gentamicin, tobramycin and amikacin. These medications are given intravenously for serious infections, gentamicin being the most common. These medications can potentially cause many serious side effects, including hearing loss and kidney damage.
Other Antibiotics
Other antibiotics used for the treatment of urinary tract infections are nitrofurantoin, fosfomycin and the carbapenems. Nitrofurantoin can be given for both treatment and prophylaxis. The advantage of this medication is that resistance is not seen even after long courses of therapy; the usual course of therapy is usually 7 to 10 days. Nitrofurantoin cannot be used to treat kidney infections. It is also not used in pregnant women within one to two weeks of delivery and nursing mothers. Fosfomycin is usually given for women who are pregnant as a one-time dose. Carbapenems--including imipenem-cilastatin, meropenem, ertapenem, and doripenem--are given by injection for UTIs. Doripenem was approved in 2007 for treatment of complicated UTIs.
References
- "Pharmacotherapy: A Pathophysiologic Approach"; Joseph T. DiPiro, Rovert L. Talbert, et al; 2008
- University of Maryland Medical Center: Urinary Tract Infections- Medications
